How does saving around $5,600 a year on energy sound for a regular family of four in a modest three bedroom house? That’s how much we saved with solar on the roof, a battery in the garage and an EV on the driveway. So how does it all break down?

We put 7kW of solar on the roof in 2021 plus a 12 kWh battery in the garage for around $35,000. Today, that money would buy around 10 kW, so a 43% bigger solar system and a Tesla Powerwall 3 rated at 13.5 kWh.

We already had an old, cheap, Nissan Leaf. The house was already well insulated and double glazed and has a whole house heat pump system. We don’t buy gas or firewood.

When the sun is shining, and even on dull days, we use the solar in the house and then charge the cars as it comes off the roof. What we don’t use charges the battery in the garage. Once that is full, it heats our hot water, and after that we get paid for selling it back to our energy retailer. All up, the sun gives us around 8,320 units of electricity per year. We sold around 2,045 kWh of that back to our retailer and made about $400.

We still buy plenty of power from our retailer, around 8,800 kWh. But because we have a battery and were paid for exporting, our total power bill for the year was just $1,700. Remember, that includes the cost of putting fuel in the EV.

One of the reasons we paid so little for all that power is because we are on a time of use tariff. This gives us three rates for peak, off-peak and nighttime consumption. Because of the battery and overnight car charging, around three quarters of the power we bought was at the cheap night rate. Just 10% was bought in the peaks. And that’s how the battery pays for itself.

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